The radio frame in the long term evolution (LTE) system includes frame structures of frequency division duplex (FDD) mode and time division duplex (TDD) mode. The frame structure of FDD mode is as shown in FIG. 1, wherein a 10 ms radio frame is composed of twenty slots with the length of 0.5 ms and numbered as 0-19, and slots 2i and 2i+1 form a subframe i with the length of 1 ms. The frame structure of TDD mode is as shown in FIG. 2, wherein a 10 ms radio frame is composed of two half frames with the length of 5 ms, each includes 5 subframes with the length of 1 ms, and subframe i is defined as 2 slots 2i and 2i+1 with the length of 0.5 ms. In the above two frame structures, as to normal cyclic prefix (Normal CP), one slot includes 7 symbols with the length of 66.7 us, wherein the CP length of the first symbol is 5.21 us, and the CP length of the remaining 6 symbols is 4.69 us; and as to an extended cyclic prefix (Extended CP), one slot includes 6 symbols, and the CP length of all the symbols is 16.67 us.
The release number of LTE corresponds to Release 8 (R8), and added release corresponds to the release number of Release 9 (R9), and as to the subsequent LTE-Advance, its release number is Release 10 (R10). The following three physical downlink control channel are defined in LTE: Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Automatic Retransmission Request Indicator Channel (PHICH), and Physical Downlink Control Channel (PDCCH).
In this case, the information carried by PCFICH is used for indicating the number of orthogonal frequency division multiplexing (OFDM) symbols of the PDCCH transmitted in a subframe, where the symbols are sent on the first OFDM symbol of the subframe, and the frequency location thereof is determined by the system downlink bandwidth and the cell identity (ID).
PHICH is used for carrying Acknowledge/Non-acknowledge (ACK/NACK) feedback information of the uplink transmission data. The number and time frequency location of PHICH can be determined by the system message and cell ID in a physical broadcast channel (PBCH) of a downlink carrier where PHICH is located.
PDCCH is used for carrying downlink control information (DCI), including uplink scheduling information, downlink scheduling information, and uplink power control information. The formats of DCI are divided into: DCI format 0, DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D, DCI format 2, DCI format 2A, DCI format 3, DCI format 3A, etc., wherein:
DCI format 0 is used for indicating the scheduling of the physical uplink shared channel (PUSCH);
DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D are used for different scheduling modes of one PDSCH codeword;
DCI format 2, DCI format 2A, and DCI format 2B are used for different space division multiplexing modes;
DCI format 3 and DCI format 3A are used for different modes of physical uplink control channel (PUCCH) and power control instructions of PUSCH.
In this case, for different bandwidths, the size of the information domain of each DCI format is as shown in Table 1:
TABLE 11.4 MHz3 MHz5 MHz10 MHz15 MHz20 MHzFormat 0/1A212225272728Format 1192327313339Format 1B222527282930Format 1C81012131415Format 1D222527282930Format 2313439434551Format 2A283136414248Format 2B252833383945Format 3/3A212225272728
The physical resources transmitted by the physical downlink control channel are in the unit of control channel element (CCE), the size of one CCE is 9 resource element groups (REG), i.e. 36 resource elements, and one PDCCH may occupy 1, 2, 4, or 8 CCEs. As to the sizes of these four types of PDCCHs occupying 1, 2, 4, or 8 CCEs, tree aggregation is used, i.e. the PDCCH occupying 1 CCE can start from any CCE location; the PDCCH occupying 2 CCEs starts from even CCE location; the PDCCH occupying 4 CCEs starts from the CCE location which is an integral multiple of 4; and the PDCCH occupying 8 CCEs starts from the CCE location which is an integral multiple of 8.
Each aggregation level defines a search space, including common search space and user equipment-specific (UE-Specific) search space. The number of CCEs of the entire search space is determined by the number of OFDM symbols occupied by the control area indicated by PCFICH in each downlink subframe and the number of PHICH groups. UE carries out blind detection on all the possible PDCCH code rates according to the DCI formats of the transmission modes in the search space.
In the kth subframe, the control domain carrying PDCCH is composed of a group of NCCE, k CCEs numbered from 0 to NCCE, k−1. UE should detect a group of PDCCH candidates in each non-discontinuous reception (non-DRX) subframes so as to acquire control information, and the detection refers to decoding the PDCCHs in the group according to all the DCI formats to be detected. The PDCCH candidates to be detected is defined in the manner of search space, and as to the aggregation level Lε{1, 2, 4, 8}, the search space Sk(L) is defined by a group of PDCCH candidates. The CCE corresponding to PDCCH candidate m in the search space Sk(L) is defined by the following formula:L·{(Yk+m)mod └NCCE,k/L┘}+i, 
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L).
As to the common search space, Yk=0, L takes the values of 4 and 8.
As to UE-specific search space, L takes the values of 1, 2, 4, and 8.Yk=(A·Yk-1)mod D, 
Where Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, └ ┘ represents round down, and ns is a slot number in a radio frame. nRNTI is the corresponding radio network temporary identifier (RNTI).
UE should detect each of the common search spaces with the aggregation levels of 4 and 8 and each of the UE-specific search spaces with the aggregation levels of 1, 2, 4 and 8, and the common search spaces and UE-specific search spaces may be overlapped. The detection times and the corresponding search spaces are as shown in Table 2:
TABLE 2Search space Sk(L)Number of PDCCHTypeAggregation level LSize [in CCEs]candidates M(L)UE-specific16621264828162Common41648162
UE is configured to receive the PDSCH data transmission according to the instruction of the PDCCH of the UE-specific search space based on one of the following transmission modes semi-statically by way of a high layer signaling:
Mode 1: Single-antenna port; port 0
Mode 2: Transmit diversity
Mode 3: Open-loop spatial multiplexing
Mode 4: Closed-loop spatial multiplexing
Mode 5: Multi-user Multi-Input Multi-Output (Multi-user MIMO)
Mode 6: Closed-loop Rank=1 pre-coding
Mode 7: Single-antenna port; port 5
If the UE is configured by the high layer to decode the PDCCH using the cyclic redundancy check (CRC) scrambled by cell radio network temporary identifier (C-RNTI), then the UE shall decode the PDCCH and all the relevant PDSCHs according to the corresponding combination defined in Table 3:
TABLE 3UE downlinkCorresponding PDSCHtransmissiontransmissionmodeDCI formatSearch spacesolution of PDCCHMode 1DCI formatCommon andSingle-antenna port1AC-RNTI-definedPort 0UE specificDCI formatC-RNTI-definedSingle-antenna port1UE specificPort 0Mode 2DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatC-RNTI-definedTransmit diversity1UE specificMode 3DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatC-RNTI-definedOpen-loop spatial2AUE specificmultiplexing ortransmit diversityMode 4DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatC-RNTI-definedClosed-loop spatial2UE specificmultiplexing ortransmit diversityMode 5DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatC-RNTI-definedMulti-user MIMO1DUE specificMode 6DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatC-RNTI-definedClosed-loop Rank =1BUE specific1 precodingClosed-loop Rank =1 precodingMode 7DCI formatCommon andIf the number of PBCH1AC-RNTI-definedantenna ports is 1,UE specificemploy single-antennaport, port 0, otherwise,transmit diversityDCI formatC-RNTI-definedSingle-antenna port1UE specificPort 5Mode 8DCI formatCommon andIf the number of PBCH1AC-RNTI-definedantenna ports is 1,UE specificemploy single-antennaport, port 0, otherwise,transmit diversityDCI formatC-RNTI-defineddual-layer transmission2BUE specificPorts 7 and 8or single-antenna portPort 7 or 8
If the UE is configured by the high layer to decode the PDCCH using the CRC scrambled by the semi-persistently scheduled cell radio network temporary identifier (SPS C-RNTI), then the UE shall decode the PDCCH and all the relevant PDSCHs according to the corresponding combination defined in Table 4:
TABLE 4UE downlinkCorresponding PDSCHtransmissiontransmissionmodeDCI formatSearch spacesolution of PDCCHMode 1DCI formatCommon andSingle-antenna port1AC-RNTI-definedPort 0UE specificDCI formatC-RNTI-definedSingle-antenna port1UE specificPort 0Mode 2DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatUE specific byTransmit diversity1C-RNTIMode 3DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificDCI formatC-RNTI-definedTransmit diversity2AUE specificMode 4DCI formatCommon andTransmit diversity1AC-RNTI-defineduser specificDCI formatC-RNTI-definedTransmit diversity2UE specificMode 5DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificMode 6DCI formatCommon andTransmit diversity1AC-RNTI-definedUE specificMode 7DCI formatCommon andSingle-antenna port1AC-RNTI-definedPort 5UE specificDCI formatC-RNTI-definedSingle-antenna port1UE specificPort 5Mode 8DCI formatCommon andSingle-antenna port1AC-RNTI-definedPort 7UE specificDCI formatC-RNTI-definedSingle-antenna port2BUE specificPort 7 or 8
If the UE is configured by the high layer to decode the PDCCH using the CRC scrambled by transmit power control—cell radio network temporary identifier (TPC-PUCCH-RNTI), then the UE shall decode the PDCCH according to the corresponding combination defined in Table 5:
TABLE 5DCI formatSearch spaceDCI format 3/3ACommon search space
If the UE is configured by the high layer to decode the PDCCH using the CRC scrambled by transmit power control-uplink shared channel-cell radio network temporary identifier (TPC-PUSCH-RNTI), then the UE shall decode the PDCCH according to the corresponding combination defined in Table 6.
TABLE 6DCI formatSearch spaceDCI format 3/3ACommon search space
Since the LTE-Advanced network needs to be able to be accessed by the LTE users, the operating frequency band thereof needs to cover the current LTE frequency band. There is already no continuous 100 MHz frequency spectrum bandwidth which can be allocated on this band, so a direct technique to be solved by LTE-Advanced is to aggregate several continuous component carriers (frequency spectrum) distributed on different frequency ranges using the carrier aggregation technology to form a 100 MHz bandwidth which can be used by LTE-Advanced. That is, as to the aggregated frequency spectrum, it is divided into n component carrier frequencies (frequency spectrums), and the frequency spectrum in each component carrier frequency (frequency spectrum) is continuous.
3GPP is set in the carrier aggregation scenario, and can schedule a plurality of component carriers in the manner of across component carrier scheduling, i.e. it can monitor the downlink control channels (PDCCH) of other component carriers on one certain component carrier. Then, it is necessary to add a carrier indicator field (CIF) in the downlink control information format (DCI format) to determine the monitored PDCCH is the PDCCH of which component carrier. For different bandwidths, the size of the information domain of each DCI format after CIF has been added therein is as shown in Table 7:
TABLE 71.4 MHz3 MHz5 MHz10 MHz15 MHz20 MHzFormat 0/1A232527293031Format 1222730343642Format 1B252829313333Format 1C81012131415Format 1D252829313333Format 2343742464854Format 2A313439434551Format 2B283136414248Format 3/3A212225272728
The 60th congress of 3GPP RAN1 physical layer obtains the decision that no CIF would be added into the common search space for DCI format 0 and DCI format 1A, but CIF can be added into the user-specific search space. It can be seen from Tables 1 and 7 that under different bandwidths, the size of the information domain of DCI format 0 and DCI format 1A with no CIF being added and that of the information domain of one certain or few certain DCI formats with CIF being added may be the same, thus, the overlapped portion of the common search space and the user-specific search space will have two or more DCI formats with the same size of information domain, which will affect the PDCCH monitoring. However, there is still no method for solving this problem in the related art, which brings inconvenience to the actual application.
At the same time, when enabling scheduling across carriers, the search space of the component carriers which is scheduled across component carriers can be enlarged, and as to how to enlarge the search space, there is still no clear solution to solve this problem currently, bringing inconvenience to the actual application.
Content of the Invention
The technical problem to be solved by the present invention is to provide a method and apparatus for detecting downlink control information, so as to solve the overlap problem of common search space and user-specific search space in Release 10 and solves the block rate problem in the situation of scheduling across carriers being enabled in Release 10.
In order to solve the above problem, the present invention provides a method for detecting downlink control information, comprising:
when scheduling across carriers is enabled, determining by a user equipment a user-specific search space monitoring a physical downlink control channel (PDCCH) according to component carrier indexes, wherein the component carrier indexes comprise component carrier indexes corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers.
Relative positions among starting positions of the user-specific search spaces corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers are fixed.
The step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes comprises:
determining a control channel element (CCE) corresponding to a PDCCH candidate m in the user-specific search space Sk(L) according to the following formula:L·{(Yk+m+ƒ(L,I))mod └NCCE,k/L┘}+i Yk=(A·Yk-1)mod D; 
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), k=└ns/2┘, └ ┘ represents round down, ns is a timeslot number in a radio frame, Y−1=nRNTI≠0, A=39827, D=65537, nRNTI is a corresponding radio network temporary identifier, NCCE, k is the number of CCEs of a PDCCH control domain carried by the kth subframe, and ƒ(L, I) is a function with input thereof being component carrier index I and aggregation level L.
      f    ⁡          (              L        ,        I            )        =            N      L        ·    I  or ƒ(L, I)=M(L)·I, wherein N is a multiple of L.
Within different subframes, generation manners of the user-specific search spaces corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers are different from each other.
The step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes comprises: determining a control channel element (CCE) corresponding to the PDCCH candidate m in the user-specific search space Sk(L) according to the following formula:L·{(Yk+m)mod └NCCE,k/L┘}+i Yk=(A·(Yk-1+ƒ(I))mod D 
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, └ ┘ represents round down, ns is a timeslot number in a radio frame, nRNTI is a corresponding radio network temporary identifier, NCCE, k is the number of CCEs of a PDCCH control domain carried by the kth subframe, and ƒ(I) is a function with input thereof being component carrier index I.
Initial configurations generated by the user-specific search spaces corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers are different from each other.
The step of determining by a user equipment a search space monitoring a physical downlink control channel according to component carrier indexes comprises:
determining a control channel element (CCE) corresponding to a PDCCH candidate m in the user-specific search space Sk(L) according to the following formula:L·{(Yk+m)mod └NCCE,k/L┘}+i Yk=(A·Yk-1)mod D,Y−1=nRNTI+ƒ(I)≠0;
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), A=39827, D=65537, k=└ns/2┘, └ ┘ represents round down, ns is a timeslot number in a radio frame, nRNTI is a corresponding radio network temporary identifier, NCCE, k is the number of CCEs of a PDCCH control domain carried by the kth subframe, and ƒ(I) is a function with input thereof being component carrier index I.ƒ(I)=216·I. 
The component carrier indexes of various component carriers are configured according to the following manner:
setting the component carrier index of the component carrier implementing scheduling across carriers as a designated value, and configuring the component carrier indexes of the various remaining component carriers being scheduled across carriers sequentially subsequent to the designated value from high to low or from low to high according to the frequency point locations thereof, with the designated value being 0;
or, configuring the component carrier indexes of the various component carriers implementing scheduling across carriers and being scheduled across carriers from high to low or from low to high according to frequency point locations thereof;
or, randomly configuring component carrier indexes for the various component carriers implementing scheduling across carriers and being scheduled across carriers;
or, configuring component carrier indexes according to carrier indication domains corresponding to the various component carriers implementing scheduling across carriers and being scheduled across carriers.
Before the step of determining by a user equipment user-specific search space monitoring a PDCCH according to component carrier indexes, the method further comprises:
judging by the user equipment whether there are at least two continuous component carriers with bands thereof being less than or equal to a designated frequency bandwidth after being aggregated in the component carriers implementing scheduling across carriers and being scheduled across carriers,
if yes, then the user equipment not determining the user-specific search space monitoring the PDCCH according to the component carrier indexes; and
if no, then the user equipment determining the user-specific search space monitoring the PDCCH according to the component carrier indexes.
When scheduling across carriers is enabled, on the component carriers implementing scheduling across carriers, the common search space when the user equipment monitors the PDCCH is N times of the common search space corresponding to the component carriers implementing scheduling across carriers, wherein N is not greater than a sum of the number of component carriers implementing scheduling across carriers and the number of component carriers being scheduled across carriers.
When sizes of the information domains of downlink control information formats configured on the component carriers implementing scheduling across carriers and component carriers being scheduled across carriers are different, after the step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes, the method further comprises: monitoring the PDCCH by the user equipment for the various component carriers on an independent search space of the various component carriers.
When sizes of the information domains of downlink control information formats configured on the component carriers implementing scheduling across carriers and component carriers being scheduled across carriers are the same, after the step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes, the method further comprises: monitoring the PDCCH by the user equipment for the various component carriers on a shared search space, with the shared search space including search space composed of the search spaces of the various component carriers.
When scheduling across carriers is enabled, if size of information domain of a downlink control information format (DCI format) under a user-specific search space condition is the same as that of the DCI format under a common search space condition, and the DCI format under the user-specific search space condition and the DCI format under the common search space condition employ the same cyclic redundancy checksum scrambled by a radio network temporary identifier, the PDCCH monitoring is carried out only according to the DCI format of the common search space, or the PDCCH monitoring is carried out only according to the DCI format of the user-specific search space.
In order to solve the above problem, the present invention also provides a method for detecting downlink control information, comprising:
when scheduling across carriers is enabled, if size of an information domain of a downlink control information format (DCI format) under a user-specific search space condition is the same as that of the DCI format under a common search space condition, and the DCI format under the user-specific search space condition and the DCI format under the common search space condition employ cyclic redundancy check scrambled by the same radio network temporary identifier, adding bits into the DCI format in the user-specific search space so that the information domain of the DCI format under the user-specific search space condition is different from that of the DCI format under the common search space condition; and
carrying out by the user equipment downlink control information detection according to the size of the information domain of the DCI format after the bits have been added therein.
The step of adding bits comprises adding one or more zero bits.
In order to solve the above problem, the present invention also provides a user equipment, configured to: when scheduling across carriers is enabled, determine a user-specific search space monitoring a physical downlink control channel (PDCCH) according to component carrier indexes, wherein the component carrier indexes comprise component carrier indexes corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers.
The user equipment is configured to determine a control channel element (CCE) corresponding to a PDCCH candidate m in the user-specific search space Sk(L) according to the following formula:L·{(Yk+m+ƒ(L,I))mod └NCCE,k/L┘}+i Yk=(A·Yk-1)mod D; 
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), k=└ns/2┘, └ ┘ represents round down, ns is a timeslot number in a radio frame, Y−1=nRNTI≠0, A=39827, D=65537, nRNTI is a corresponding radio network temporary identifier, NCCE, k is the number of CCEs of a PDCCH control domain carried by the kth subframe, and ƒ(L, I) is a function with the input thereof being component carrier index I and aggregation level L.
      f    ⁡          (              L        ,        I            )        =            N      L        ·    I  or ƒ(L, I)=M(L)·I, wherein N is a multiple of L.
The user equipment is configured to determine a control channel element (CCE) corresponding to a PDCCH candidate m in the user-specific search space Sk(L) according to the following formula:L·{(Yk+m)mod └NCCE,k/L┘}+i Yk=(A·(Yk-1+ƒ(I))mod D 
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, └ ┘ represents round down, ns is a timeslot number in a radio frame, nRNTI is a corresponding radio network temporary identifier, ƒ(I) is a function with the input thereof being component carrier index I, and NCCE, k is the number of CCEs of a PDCCH control domain carried by the kth subframe.
The user equipment is configured to determine a control channel element (CCE) corresponding to a PDCCH candidate m in the user-specific search space Sk(L according to the following formula:L·{(Yk+m)mod └NCCE,k/L┘}+i Yk=(A·Yk-1)mod D,Y−1=nRNTI+ƒ(I)≠0;
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), A=39827, D=65537 k=└ns/2┘, └ ┘ represents round down, ns is a timeslot number in a radio frame, nRNTI is a corresponding radio network temporary identifier, ƒ(I) is a function with the input thereof being component carrier index I, NCCE, k is the number of CCEs of a PDCCH control domain carried by the kth subframe.ƒ(I)=216·I. 
The user equipment is further configured to: receive the component carrier indexes of the various component carriers configured according to the following manner:
setting the component carrier index of the component carrier implementing scheduling across carriers as a designated value, with the designated value being 0, and sequentially configuring the component carrier indexes for the various remaining component carriers being scheduled across carriers subsequent to the designated value from high to low or from low to high according to frequency point locations thereof;
or, configuring the component carrier indexes of the various component carriers implementing scheduling across carriers and being scheduled across carriers from high to low or from low to high according to the frequency point locations thereof;
or, randomly configuring component carrier indexes for the various component carriers implementing scheduling across carriers and being scheduled across carriers;
or, configuring component carrier indexes according to carrier indication domains corresponding to the various component carriers implementing scheduling across carriers and being scheduled across carriers.
The user equipment is further configured to: before determining the search space for PDCCH monitoring according to the component carrier indexes, judge whether there are at least two continuous component carriers with bands thereof being less than or equal to a designated frequency bandwidth after being aggregated in the component carriers implementing scheduling across carriers and being scheduled across carriers, if yes, then the user equipment does not determine the search space for the PDCCH monitoring according to the component carrier indexes; and if no, then the user equipment determines the search space for the PDCCH monitoring according to the component carrier indexes.
When scheduling across carriers is enabled, on the component carriers implementing scheduling across carriers, a common search space when the user equipment monitors the PDCCH is N times of the common search space corresponding to the component carriers implementing scheduling across carriers, wherein N is not greater than a sum of the number of component carriers implementing scheduling across carriers and the number of component carriers being scheduled across carriers.
The user equipment is further configured to: when sizes of information domains of downlink control information formats configured on the component carriers implementing scheduling across carriers and component carriers being scheduled across carriers are different, after having determined the user-specific search space monitoring the physical downlink control channel according to the component carrier indexes, carry out PDCCH monitoring on the various component carriers on an independent search space of the various component carriers.
The user equipment is further configured to: when sizes of information domains of downlink control information formats configured on the component carriers implementing scheduling across carriers and component carriers being scheduled across carriers are same, after having determined the user-specific search space monitoring the physical downlink control channel according to the component carrier indexes, carry out PDCCH monitoring on the various component carriers on a shared search space, with the shared search space including a search space composed of the search space of the various component carriers.
The user equipment is further configured to: when scheduling across carriers is enabled, if size of information domain of a downlink control information format (DCI format) under a user-specific search space condition is the same as that of the DCI format under a common search space condition, and the DCI format under the user-specific search space condition and the DCI format under the common search space condition employ cyclic redundancy check scrambled by a same radio network temporary identifier, carry out PDCCH monitoring only according to the DCI format of the common search space, or carry out PDCCH monitoring only according to the DCI format of the user-specific search space.
In order to solve the above problem, the present invention also provides an apparatus for detecting downlink control information, comprising a network side device and a user equipment, wherein:
the network side device is configured to: when scheduling across carriers is enabled, if size of an information domain of a downlink control information format (DCI format) under a user-specific search space condition is the same as that of the DCI format under a common search space condition, and the DCI format under the user-specific search space condition and the DCI format under the common search space condition employ cyclic redundancy check scrambled by a same radio network temporary identifier, add bits into the DCI format in the user-specific search space so that the information domain of the DCI format under the user-specific search space condition is different from that of the DCI format under the common search space condition; and
the user equipment is configured to: carry out downlink control information detection according to the size of the information domain of the DCI format after the bits have been added therein.
The network side device is configured to add bits according to the following manner: add one or more zero bits.
In order to solve the above problem, the present invention also provides a network side device, configured to:
when scheduling across carriers is enabled, if size of information domain of a downlink control information format (DCI format) under a user-specific search space condition is the same as that of the DCI format under a common search space condition, and the DCI format under the user-specific search space condition and the DCI format under the common search space condition employ cyclic redundancy check scrambled by a same radio network temporary identifier, add bits into the DCI format in the user-specific search space so that the information domain of the DCI format under the user-specific search space condition is different from that of the DCI format under the common search space condition and the user equipment carries out downlink control information detection according to the size of the information domain of the DCI format after bits have been added therein.
The network side device is configured to add bits according to the following manner: add one or more zero bits.
In summary, the present invention solves the problem of the PDCCH monitoring at the UE end due to that the size of the information domain of the DCI format under the user-specific search space condition and that of the information domain of the DCI format under the common search space condition may be the same when scheduling across carriers is enabled in the LTE-Advanced carrier aggregation scenario. Moreover, the problem that how to define the search space for the UE to detect the PDCCH when scheduling across carriers is enabled is solved.